With the advent of fuel injection for internal combustion engines, it has become common to mount electrically operated fuel pumps in the fuel tank of a vehicle. These pumps, though quite small, rotate at high rates of speed. Any unbalance in the pump, or a condition called cavitation, or pulsations of the pumping element, can cause noise and vibration of the pump housing. Since the fuel tank is usually mounted at the area of a passenger compartment of a vehicle, this noise or vibration can be a source of discomfort or irritation to passengers.
It is, therefore, desirable to mount the pump in a way which will reduce the transmission of noise and vibration to a minimum and render it generally imperceptible to passengers. The pump design is involved in this reduction but also the mounting of the pump.
U.S. Pat. Nos. 4,590,964 (Beardmore) and 4,591,319 (Takahashi et al) are directed to this problem of noise and vibration in the use of rubber mounting elements. U.S. Pat. No. 3,659,965 (Ebert et al) shows a combination of an elastomeric housing over a coil spring. Leaf spring mounts for motors are illustrated in U.S. Pat. No. 3,145,910 (Jolly) and 3,538,357 (Barthalon). U. S. Pat. No. 4,569,637 (Tuckey) shows a metallic outer shell with rubber end mounts.
The present invention is directed to a mounting system for a fuel pump designed to reduce noise and vibration in a relatively simple structure which avoids the use of any rubber or elastomeric material, the latter being subject to deterioration with continued exposure to hydrocarbon fuels. In addition, the elastomeric material spring rate also changes with temperature.
Briefly, the invention achieves the desired objects by utilizing a molded casing dimensioned oversize relative to the pump housing and formed to mount on a depending pipe provided in the fuel tank for return fuel flow from the basic pumping system. Two coil springs of very low natural frequency with axially diminishing diameters are provided at each end of the pump housing to mount the housing in the casing for resilient motion axially and radially. A flexible outlet conduit from the pump conducts fuel through the top of the tank to a fuel supply conduit leading to a vehicle engine.
Other objects and features of the invention will be apparent in the following description and claims in which the principles of the invention are set forth together with details to enable persons skilled in the art to practice the invention all in connection with the best mode presently contemplated for the invention.